X-ray beams can be used for characterizing a large range of materials including materials used in the semiconductor industry. Various methods have been developed for generating X-ray beams. For example, U.S. Pat. No. 7,257,193, to Radley, et al., whose disclosure is incorporated herein by reference, describes an X-ray source assembly having enhanced output stability using tube power adjustments and remote calibration. A control system is provided for maintaining intensity of the output X-rays dynamically during operation of the X-ray source assembly, notwithstanding a change in at least one operating condition of the X-ray source assembly, by changing the power level supplied to the assembly.
European Patent 2,050,100, to Boulee, et al., whose disclosure is incorporated herein by reference, describes a system for delivering an X-ray beam, comprising a source block that emits a source X-ray beam and conditioning means for conditioning the source beam sent towards a specimen. The system includes stabilization means designed to thermally stabilize a region of the system lying downstream of the source block, in order to limit heat transfer towards the conditioning means for the purpose of preventing thermal perturbations in the conditioning means.
U.S. Pat. No. 6,282,263, to Arndt, et al., whose disclosure is incorporated herein by reference, describes an X-ray generator which produces an X-ray source having a focal spot or line of very small dimensions and which is capable of producing a high intensity X-ray beam at a relatively small point of application using a low operating power.
U.S. Pat. No. 6,788,633, to Loxley, et al., whose disclosure is incorporated herein by reference, describes a method and apparatus for prolonging the life of an X-ray target. An X-ray generator comprises an evacuated and sealed X-ray tube, containing an electron gun and an X-ray target. An electron beam is produced by the electron gun in which the cathode is at negative high voltage, the electron gun consisting of a filament just inside the aperture of a Wehnelt grid which is biased negatively with respect to the filament.
U.S. Pat. No. 4,675,890, to Plessis, et al., whose disclosure is incorporated herein by reference, describes an X-ray tube for producing a high-efficiency beam and especially a pencil beam as applicable to the field of radiology and more especially digital radiology, comprises an anode provided with a rectilinear bore and a cathode for generating an electron beam which enters the bore. The internal walls of the bore constitute an anode target which is bombarded by the electron beam in order to produce at least one x-ray beam which emerges from one end of the bore.
U.S. Pat. No. 5,148,462, to Spitsyn, et al., whose disclosure is incorporated herein by reference, describes formation of high thermal conductivity X-ray anode sources for production of high intensity X-rays. The anode sources are structures containing diamond (passive element) and desired target material(s) consisting of metal(s) and (or) their alloys for the generation of high intensity X-radiation of the desired wavelength.